Physiological responses to Tai Chi in stable patients with COPD

• Respiratory muscle work was compared between Tai Chi and treadmill exercise.
• Tai Chi was an acceptable exercise modality for pulmonary rehabilitation.
• Dynamic hyperinflation after Tai Chi was less severe than after treadmill exercise.
• Tai Chi induced low frequency quadriceps fatigue.

We compared the physiological work, judged by oxygen uptake, esophageal pressure swing and diaphragm electromyography, elicited by Tai Chi compared with that elicited by constant rate treadmill walking at 60% of maximal load in eleven patients with COPD (Mean FEV1 61% predicted, FEV1/FVC 47%). Dynamic hyperinflation was assessed by inspiratory capacity and twitch quadriceps tension (TwQ) elicited by supramaximal magnetic stimulation of the femoral nerve was also measured before and after both exercises.The EMGdi and esophageal pressure at the end of exercise were similar for both treadmill exercise and Tai Chi (0.109 ± 0.047 mV vs 0.118 ± 0.061 mV for EMGdi and 22.3 ± 7.1 cmH2O vs 21.9 ± 8.1 cmH2O for esophageal pressure). Moreover the mean values of oxygen uptake during Tai Chi and treadmill exercise did not differ significantly: 11.3 ml/kg/min (51.1% of maximal oxygen uptake derived from incremental exercise) and 13.4 ml/kg/min (52.5%) respectively, p > 0.05. Respiratory rate during Tai Chi was significantly lower than that during treadmill exercise. Both Tai Chi and treadmill exercise elicited a fall in IC at end exercise, indicating dynamic hyperinflation, but this was statistically significant only after treadmill exercise. TwQ decreased significantly after Tai Chi but not after treadmill.We conclude that Tai Chi constitutes a physiologically similar stimulus to treadmill exercise and may therefore be an acceptable modality for pulmonary rehabilitation which may be culturally more acceptable in some parts of the world.